Nationally representative surveys of pregnant women show that, in the past month, 5.4% report use of illicit substances, 9.4% report use of alcohol, and 15.4% report smoking cigarettes. Further, since 2000 there has been nearly a five-fold increase in maternal use of opioids during pregnancy. These statistics are likely to be underestimates given that they are based upon self-report and because of stigma and fear, many women under-report their use of hazardous substances in pregnancy. Screening measures for identifying alcohol use in pregnancy are relatively well developed but this is not the case for illicit drug use or prescription drug misuse. The availability of well-performing screening tools for substance use in pregnancy can help clinicians identify patients who could benefit from additional assistance and resources. The study proposed in this application has been carefully designed to validate and compare screening tools for maternal substance use. The study would be led by a team of investigators from the Yale School of Medicine, Wayne State University and Harvard University. This team has extensive experience developing and evaluating substance use screeners that are relevant for pregnant women. The study cohort would be assembled from clinical centers that in their totality are representative of pregnant women in terms of race, ethnicity, socioeconomic status and substance use. We would use an innovative two-phase approach that would screen women anonymously but also address response set/expectations in participants. All participants would be offered referrals for treatment. We would use a gold standard that is derived from participant self-report and urine toxicology screens. Analyses would describe the measurements of merit for all screeners, compare their performance and would use available data to generate a new measure that may have superior performance compared to existing screeners. The work from this project would be used to develop materials that can be used to facilitate the use of these measures into clinical settings. Overall, this project has a high likelihood of benefitting the health of women and their children and of being of value to clinicians who care for pregnant women.